Taichi "Tai" Kamiya recounts how the world's climate has been going haywire—Asia is in a drought, the Middle East is being hit by flash floods, and America is wracked with freezing cold temperatures. Meanwhile, he's in summer camp, having a perfectly normal summer until it begins snowing, and a sudden blizzard appears.

Tai and his friends, Sora Takenouchi, Yamato "Matt" Ishida, Koushiro "Izzy" Izumi, Mimi Tachikawa, Takeru "T.K." Takaishi, and Joe Kido, are all amazed when it begins snowing. They then observe lights like auroras in the sky, from which emerges a portal that shoots out strange electronic devices. When they reach out and grab the objects, a huge wave of water erupts from the ground and sucks them into the portal, which sends them to a new world.

Tai is awoken by a strange creature which calls itself Koromon, and soon Izzy shows up with his own creature, Motimon. The creatures claim to know Tai and Izzy, and to have been waiting a long time for them.

The kids try to figure out where they are, and Tai climbs a tree to take a look through his telescope. He's startled to find that they are near the ocean, and then spots a huge red beetle, which Koromon tells him is Kuwagamon. It attacks Tai and Izzy, but they hide within a "hiding tree", which is partially a hologram. After Kuwagamon passes, Sora tells them to come out, and the group is reunited and introduced to each child's new creature. Sora has Yokomon. T.K. has Tokomon whom he instantly hits it off with. Matt has Tsunomon. Joe has Bukamon whom he is afraid of. The creatures then explain that they are "Digimon: Digital Monsters!".

As the group wonders where Mimi is, they hear her screaming and spot her and her Tanemon being chased by Kuwagamon. It chases the gang to the edge of a cliff, and the Digimon decide to fight, despite the children wanting to flee. However, as In-Training Digimon, they can only blow bubbles, and are knocked out by the Champion-level Kuwagamon. The children try to stop them from fighting, and just as everything seems lost, the devices glow and the Digimon suddenly digivolve to Rookie level! Koromon becomes Agumon, Yokomon becomes Biyomon, Motimon becomes Tentomon, Tsunomon becomes Gabumon, Tokomon becomes Patamon, Bukamon becomes Gomamon, and Tanemon becomes Palmon. While the humans are shocked by the transformation, the seven Rookie Digimon begin attacking Kuwagamon, but even their combined attacks are only enough to daze it. It crashes into the cliff, breaking off the chunk the kids and Digimon are on and letting it fall into the river.